The present invention relates to gypsum boards and a method for manufacturing the same.
A gypsum board is an inflammable construction material made of a core material of gypsum which is covered with base paper to form a board. It is widely used as an interior finish material for walls and ceilings of buildings. However, troubles often occur during handling as the base paper easily peels off the gypsum core material. In conventional manufacturing processes a slurry containing calcined gypsum as the main component is directly poured between two sheets of base paper, molded and hardened to cause the core material to adhere to the base paper. The adhesion thus obtained, however, has not been satisfactory. Light-weight gypsum board which is manufactured by mixing a large amount of air bubbles in the slurry is particularly defective as the base paper is very likely to peel off from the gypsum core material because of smaller contact area between the slurry and paper. Various methods have been proposed to improve the adhesion such as by impregnating the base paper with soluble phosphate (Jap. Pat. Pub. No. Sho-53-28173), by coating the surface of the base paper previously with an aqueous solution containing water soluble substance or a water emulsion of calcined gypsum mixed (Jap. Pat. Pub. No. Sho-42-27679), etc., but these methods do not necessarily provide satisfactory adhesion. For example, an aqueous solution of a water soluble substance is absorbed by the base paper causing only negative effect. The water emulsion of calcined gypsum is also defective as it tends to migrate into the slurry mainly containing the calcined gypsum to be used as the core material thereby offsetting the intended effect.